He appeared to be quite casually shooting the breeze with the other officer. I’m not disputing what you say, but he sure as hell didn’t look injured.
The photo of Wilson at the bottom of the page (next to Brown's), is taken from when he received a police commendation back in February:
From the video photos, I'd be hard-pressed to figure out who those officers are. The video is very blurred, and any injuries to either one of their faces wouldn't be apparent. Not sure if there's any other photos out there that are clearer. These photos are immediately after the incident, and any injuries may not even be visible yet, ie., black and bluing.